Disappearance of factor VIII autoantibodies preceding autoimmune haemolytic anaemia.

We describe a previously healthy woman who at the age of 44 years developed a factor VIII inhibitor, that over the years increased to a maximum level of 3600 Bethesda units (BU) mL(-1) in 1978. The epitope specificity of the factor VIII inhibitor was investigated and antibodies directed against the A2 and C2 domains of factor VIII were detected. The majority of these antibodies were of subclass IgG4. Over the years, the inhibitor titre gradually decreased and in 1989, the inhibitor could no longer be detected. Shortly after, the patient developed autoimmune haemolytic anaemia. A possible link between the disappearance of factor VIII inhibitors and the development of other autoantibodies may be explained by concomitant development of anti-idiotypic antibodies that neutralize the activity of factor VIII inhibitors. We were unable to detect anti-idiotypic antibodies, which could explain the decline in factor VIII inhibitor titre in this patient.

Evaluation of an automated hemostasis testing analyzer, the Trombolyzer Combi.

We evaluated the Trombolyzer Combi (Behnk Elektronik, Norderstedt, Germany), an automated hemostasis analyzer, in a clinical setting. Determination of prothrombin time (PT), activated partial prothrombin time (APTT), fibrinogen (FIB) and antithrombin (AT) were performed using Organon Teknika reagents. Determination of PT, APTT and FIB on a KC4 (Amelung, Germany) using Dade reagent (Dade Behring, The Netherlands) and determination of AT on a Hitachi 912 using Chromogenix reagent (Nodia, The Netherlands) were used as reference methods. Within-run and total precision of the tests were determined by measuring pooled plasma samples at various levels in duplicate twice daily for twenty days. For all tests the within-run and total precision of the Trombolyzer Combi was comparable or superior to the reference methods. Methods comparison was performed with 100 patient samples for PT, APTT and FIB and with 50 patient samples for AT. The correlation coefficients between the Trombolyzer Combi values and the results from the reference methods were between 0.87 and 0.98. No effect of hemolysis on the determination of the studied parameters was detected. However, bilirubinemia above 260 micromol/L and triglycerides above 9 mmol/L resulted in erroneous test results. In conclusion, it is shown that the Trombolyzer Combi performs equivalently or better than the reference methods and can be used as a state-of-the-art hemostasis analyzer in a clinical laboratory.